The entire narrative is a memory piece, told by an elderly Zero Moustafa, who reveals how he, a penniless lobby boy, came to own the once-magnificent hotel. The central mystery is solved when Gustave and Zero, after a frantic chase, retrieve the "Boy with Apple" painting. Taped to its back is a second, superseding will from Madame D., confessing that she was the secret owner of the Grand Budapest and bequeathing her entire fortune, including the hotel, to Gustave in the event she was murdered. This clears Gustave's name, and Dmitri is forced to flee.
However, this triumphant moment is immediately undercut by tragedy. The film's whimsical tone abruptly shifts as Zero recounts the subsequent events with devastating brevity. A few years later, after Zero and Agatha have married, the war has fully broken out. While traveling on a train, soldiers harass Zero. Gustave intervenes, defending his protégé with the same indignant fury as before, but this time, the soldiers are not swayed. They take him outside and execute him by firing squad. Zero explains that Gustave's entire estate, now vast, was left to him, his sole heir. In an even more heartbreaking reveal, Zero tells the Author that Agatha and their infant son died two years after Gustave from the "Prussian Grippe." The reason Zero keeps the lonely, unprofitable hotel is not because of Gustave, but because it is his last tangible link to his beloved Agatha and the short time they were happy there together.